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Sun Sep 18, 2022, 03:36 PM

These Trees Are Spreading North in Alaska. That's Not Good [View all]


The white spruce colonists are likely warming the Arctic landscape too. Normally, snow cover makes these northern lands reflect the sun’s energy back into space—in scientific parlance, the land’s “albedo” is high. But trees are darker, so they have a lower albedo and absorb heat, which warms the area. “The albedo effect is the big thing,” says Goetz. “They absorb a lot more energy.”

(This is also why the Arctic, in general, is warming so much faster than the rest of the planet: As sea ice disappears, it exposes darker waters underneath, which absorb more of the sun’s energy.)

Counterintuitively, by acting as a sort of snare to trap snow against the ground, a forest further heats the soil. A thick layer of snow prevents the chill of winter from penetrating into the ground, and the extra trees block cold winds. (That trapped snow also provides lots of moisture for those trees in the future, creating a feedback loop.)

Thawing permafrost is the aspect of Arctic greening that concerns scientists the most. These frozen soils are loaded with dead organic matter that hasn’t fully decomposed, but will decay rapidly once it thaws. Microbes then begin munching on the material, spewing both carbon dioxide and methane, an extremely potent greenhouse gas. Permafrost is now thawing so fast that Arctic land is collapsing, gouging great big holes in the landscape. “The implications are significant,” says Goetz. “It always comes around to the permafrost in the end, because that's the big carbon reservoir that's being mobilized.”

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Reply These Trees Are Spreading North in Alaska. That's Not Good [View all]
NickB79 Sep 2022 OP
Hermit-The-Prog Sep 2022 #1